With the advent of easy travel between far countries, the societies of the world have become more and more cosmopolitan. One area where this is best exemplified is in the proliferation of differernt types of popular foods and methods of food preparation. The modern human being has access to cuisine from myriad cultures and locales. No longer is one restricted to the same sort of food and cooking methods utilized by one's forebearers.
One type of cuisine that has become very widespread and popular is the genre of oriental, and more particularly Chinese, cooking. Even the term "Chinese cooking" is too broad since there are many subgroups within it. However, the food preparation techniques of stir frying and deep fat frying with a minimal amount of oil carry throughout. For these methods of preparation the traditional and appropriate vessel is the broad round metal vessel known as a wok.
There are many advantages to wok cooking. The concave interior (in the shape of a sector of a sphere) of a wok has no sharp corners or nooks and crannies in which food can become trapped. Therefore, it is especially well suited for cooking items evenly. The smooth cooking surface also makes it possible to cook using a minimum amount of fats or oils since the items to be cooked may be moved into the heated oil very easily. A larger usable surface area of oil may be obtained with the same volume of oil in a wok than may be attained in other frying implements such as cylindrical or flat-bottomed pots or deep fat fryers.
Woks are also typically utilized for cooking for very short time periods at high heats. In a typical stir-fry recipe the cooking time is 4 minutes or less. The health benefits of short time cooking with minimal use of fats are substantial. Less fat is absorbed into the food being cooked than with Western methods and consequently the fat intake of the diner is minimized. In addition to the health benefits, the flavor in the food items, particularly in vegetables, is substantially retained by the high temperature sealing of the surfaces. This cauterization seals the flavors and juices inside for maximum concentration.
Typical foods to be cooked in a wok, such as marinated meats and fresh vegetables, contain a significant amount of water and/or aqueous based fluids. There is also frequently some free moisture associated with the foods since they have been recently washed or marinated. When this water and other free moisture encounters the hot oil, the vaporization of the aqueous substances draws energy from the surroundings (under equilibrium principles) and causes a substantial cooling of the oil. With the small quantities of cooking oil typically utilized in Chinese cooking this can result in a very substantial temperature reduction in the cooking oil.
For this reason, Western recipes for Chinese cooking suggest that extremely high smoke-point cooking oils, such as peanut oil, be utilized. The reason for this is that these oils can be heated to nearly 500.degree. F. before beginning to degrade. The object is that if the oil is initially heated to a temperature which is very high, in relation to the necessary minimum frying temperature, then even the cooling caused by evaporating the moisture will not cause the oil to drop below the critical frying and cauterization temperature, approximately 150.degree. C. (.about.300.degree. F.).
With oils which cannot be heated to such a high temperature, the endothermic reaction of vaporization of the moisture causes the oil temperature to drop below effective cauterization levels and results in less effective sealing of the capillaries in the food. The longer the food is heated at temperatures below the cauterization temperature the more moisture is delivered from the interior of the food item, by capillary action, to the exterior and vaporized away. Thus, the longer the oil is maintained at a temperature below effective cauterization levels the more moisture is lost from the food item and the dryer and less tasty the finished meal. Therefore, it is extremely desirable to maintain minimum frying temperatures at all times or, at least, to minimize the time during which the oil temperature is below optimum levels.
The difficulties with temperature reduction affecting the drying out of the food are not as pronounced in traditional Chinese cooking not in Western cooking, regardless of the type of cooking oil utilized. In traditional Chinese style cooking the problem is avoided since the wok is in direct contact with a high volume heat source which can replenish the heat at a very rapid rate and maintain the oil at a substantial temperature. In Western cooking methods the problem does not arise because the volume of cooking oil utilized is so large that the net cooling effect from the endothermic vaporization of the moisture is widely distributed and has little net effect on the overall temperature of the oil.
The traditional wok is also very useful because it is easily cleaned between courses. The rounded smooth metal surface may be easily wiped out or dumped for cleaning with very little residue. Thus it is possible to cook multi course meals in the same vessel.
One of the main impediments to the use of the wok by modern Western cooks is that it does not adapt well to use on electric and gas ranges. The wok was developed for use in placing it directly on hollowed out sections of coals in the ground and/or on rings with a wide based fire built underneath. However, the cooking surfaces utilized in the United States, particularly, are typically flat for delivering heat to flat bottomed cooking vessels such as frying pans or sauce pans. The spherical surface of the wok does not adapt well to cooking on modern electric and gas ranges. Various methods have been utilized in attempts to overcome this problem.
Some methods have involved modifying the structure of the wok itself. One such method is the production of flat bottomed woks for resting in a stable manner on a flat range tops. This has been done either by making the wok wall a uniform thickness and having both inside and outside have a flat bottom, in which case the resultant utensil is a little more than a high sided frying pan with all its inherent disadvantages, or by building the outside of the wok up only to leave a spherical cooking surface with a flat exterior surface. The disadvantage of the second method is that the weight and mass of the wok are substantially increased. This leads to difficulties both in making the wok unwieldly for dumping cooked food out and other handling and also in substantial heat retention on the cooking surface which limits the efficacy of cleaning the wok between courses. A standard thin walled wok will cool substantially in a very short time after being removed from the heat and is thus easily cleaned whereas a wok with the material built up to form a flat bottom will retain the heat and will be much more difficult to clean.
Another modification to the wok has been the use of elelctric woks wherein the heating elements are arrayed in a partially sherical fashion about the bottom of the wok to provide even heat distribution. These woks are typically quite expensive and also retain the same disadvantages of the built up flat bottomed woks regarding unwieldliness and undue heat retention.
Those who wish to attain the advantage of cooking in a traditional thin walled wok have been forced either to abandon the use of modern ranges or else to utilize some form of interface adapter between the range and the wok. The alternate heating methods are less than desirable since they force the user to abandon the range top, the most commonly used cooking area in the kitchen. Thus, interface adapters have become popular.
The interface adapters that have been used to date have all been in the nature of rings or collars which are adapted to fit on the range element surface and to provide a circular ring upper surface into which the wok bottom nests in a fairly stable fashion. All of the rings and collars which the inventor has observed have been provided with holes for easy grasping and to reduce the total weight of the adapter.
There are three major disadvantages to prior art interface adapters. The first is thay they often lack stability. Electrical range elements are typically spiral elements with spaces between different portions of the element. In this manner, the bottom surface of the adapter ring will typically rest partially on the element and partially on the spans betwen portions of the element. Especially since the shape and size of the electrical elements varies drastically from stove to stove, this can often result in an unstable circumstance. Instability can be a great disadvantage since spillage of cooking oil can lead to kitchen fires and severe burns to the cook. The problem is even more notable in gas ranges which typically have only an open latticework frame to support the cooking vessel with wide spaces between the various elements of the frame. There is a greater danger of instability of the adapter rings on this sort of latticework than even on the electrical elements.
A second disadvantage of prior art adapter rings or collars is that the heat is delivered to the wok in an uneven fashion. Thermal energy is deliverd directly by conduction to the ring portion of the wok where the top of the adapter ring and the wok directly interface. However, the remaining portions of the wok must either be heated by radiative energy or by indirect conduction. Consequently, a hot ring area may develop part-way up the sides of the wok, particularly if the wok is constructed of less than optimal material. This provides for uneven cooking and does not provide the maximum heat to the very bottom of the wok where most of the actual cooking takes place.
A third disadvantage of prior art interface adapter rings and collars is energy inefficiency. A significant amount of thermal energy is carried away from the cooking surface of the wok both by radiation from the ring and by convection through the holes in the ring. Thus the cook is obligated to maintain the heating element at very high heat in order to achieve proper cooking temperatures on the interior of the wok. At least one major distributor (General Electric) has specifically recommended against the use of oriental woks and prior art adapters in conjunction with their stove tops (Stove Top Owners Manual, publication number 49-4523, page 6). The continual use of the high heat involved with prior arts adapters can cause damage to the stove top elements.
Additionally, the prior art interface adapter rings and collars tend to dissipate heat rapidly when the wok is removed for food dispersal and/or cleaning. Therefore, it is necessary to reheat the adapter and the wok again as soon as the wok is replaced on the ring. Substantial energy is wasted in this manner.
Furthermore, since the prior art adapters do not retain any substantial amount of heat they do not provide a high volume heat transferral mechanism to the wok. Therefore, when the cooler food substances and the associated free moisture are delivered to the oil the consequent cooling will lower the temperature of the oil below the cauterization level. Since there is no truly high volume heat source to reheat the oil quickly to the cauterization level this results in dryer and less tasty foods unless a very high smoke-point oil is utilized. Even in these cases the energy utilization is increased since it is necessary to heat the oil to a higher temperature before it is usable. Due to the inefficiency of heat transfer it is necessary to maintain the heating element or flame level at a higher increment to result in effective stir-frying.
None of the prior art attempts have been satisfactory in providing a method by which the traditional oriental wok may be properly utilized with modern Western flat topped cooking elements.